feat: add license activation system with feature gates

- License key generator tool at ~/Desktop/LicenseGenerator
- Backend validator route (GET /api/license/status, POST /api/license/activate)
- Activation page in sidebar with status, key input, and free/premium feature list
- useLicense hook for frontend license state
- Feature gates: premium eligibility buttons (DDMA, DeltaIns, Tufts, United, CCA) disabled without license
- Feature gates: premium claim buttons (CCA, Delta MA, United, Tufts) and all PreAuth buttons disabled without license
- Free features always active: MassHealth eligibility/claim, Documents, Payments, Backups, Reports
- README: license key generator usage instructions

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

README.md

@@ -387,6 +387,47 @@ Each office runs its own `cloudflared` tunnel on its own PC. Ports never conflic
 
 ---
 
+## License Key Generator
+
+The license key generator is a private tool that lives only on your dev PC. Use it to generate a new license key for any office every 3 months.
+
+**Location:** `/home/ff/Desktop/LicenseGenerator/`
+
+**Generate a 3-month key (default):**
+```bash
+node /home/ff/Desktop/LicenseGenerator/generate-license.js
+```
+
+**Generate a key with a custom duration:**
+```bash
+node /home/ff/Desktop/LicenseGenerator/generate-license.js --months=6
+```
+
+**Example output:**
+```
+=== Dental App License Key ===
+
+License Key: DENTAL-8ED7AAEF3E0CA008D98CC1E0-2026-08-26
+Expires:     2026-08-26
+Duration:    3 month(s)
+
+Paste this key into the Activation page in the app.
+```
+
+**Workflow:**
+1. Office pays renewal fee
+2. Run the generator script above
+3. Copy the License Key
+4. Paste it into the **Activation** page in the app (via RustDesk or in person)
+5. Record the key, office name, expiry, and payment in your records
+
+**Important — `secret.key`:**
+- `/home/ff/Desktop/LicenseGenerator/secret.key` is the private secret used to sign all keys
+- Back it up on a USB drive or password manager
+- If lost, all existing keys become invalid and new keys must be issued to all offices
+
+---
+
 ## Claude Code Memory
 
 Claude Code (the AI assistant used to build this project) stores its memory locally on the PC. This memory contains project context, architecture decisions, feature history, and working preferences — allowing Claude to pick up where it left off in new sessions.